This is taking from a comment I saw in the "Gnolls- come up with something, anything, interesting about them" thread. The troll lore isn't that exciting, but this is just my opinion. I want you to come up with your own head lore or whatever about trolls and how you use them. The comment in question was, "Gnolls are now a gnome-troll combination. I did this. Be happy for the gnoll option you get when first making your gnome, not knowing why it's there."

In my games, I don't have many 'monsters that are just monsters' - but trolls are one of those. They didn't build a functional society, they don't contribute in some positive way, when everyone else goes to market (orcs, goblins, ogres and so on), trolls don't. They don't grow stuff, or forge, they have no culture or history or great works of art. 

Now, propably you think trolls are a race. it makes sense: They're tool using bipeds, so how are they not a race. But ask yourself: Do you really think trolls procreate? Do you imagine that, every once in a while, a troll boy meets a troll girl, and the magic of love just happens? 

No. You do not, and neither do I.

Trolls are an infection. Or rather, troll blood is infected. It's a little bit of a mystery how it spreads precisely, but if you're lucky, I'll have it figured out by the time I finish writing. Anyways ..!

There is something in troll blood that both heals and harms. It makes you regenerate, but it eats away at everything else: Memories, intelligence, all mental aspects rot away - while your body warps and changes too. 

But wait, I hear you object - does that mean that trolls used to be human? Or elven? 

Yes, and no. The transformation from man or elf to troll is an insidious one. Stand by, as I reveal the true terror of the origin of trollism. 

The infection carried in troll blood isn't itself contagious. Or rather, the conditions for contagion aren't normally present. The contagion comes from a parcitular fungus. Every once in a while, someone will either die, slumped against a tree deep in the forest - or will be starving, and try eating fungi at random. Either way, trollism is sort of related to undeath: You have to die first, and while you're sort of no longer present, the infection works on what's left behind: It wipes away who you were, restarts the heart, and warps your body to something monstrous. 

What few realise is that ... should you try casting Ressurrection on a troll, not only may you slay the troll outright, you may save some poor soul who just ate the wrong thing in the forest because they were hungry and lost.

I did this thread a while back: https://www.dndbeyond.com/forums/d-d-beyond-general/story-lore/193039-on-the-ecology-of-trolls

From that, I'm still tinkering with the idea that enviromental conditions combined with a trolls regeneration will produce odd "evolutions" in Trolls, So a Troll that drowns effectielly drops to zero hit points and regenrates back to one hit point over and over again and eventually the troll develops gills, trolls that are subjected to fire repeatedly eventually become resistant to it etc.You can then spin that out to have mad scientist style villains trying to produce different types of Trolls, maybe have a Hydra in the area and this iis one of the villains Trollish monstrosities that has escaped?.

There was also a particualry nasty Troll variant we had in a LARP group called a Llort which was essentially the Troll version of a Nilbog (see Volo's Guide to Monsters), it tied into playing on players knowledge that if you see a Troll you break out the fire and acid but, if you used fire or acid againt the Llort it reflected the damage back against the user, it was basically immune to other damage until you turned off its regeneration ability which required you to hit it was a spell that healed damaged such as Cure Wounds. In the heat of a LARP fight this was not something you wanted to have to get your head around.

Although templates don't really exsist in 5e there was a Half Troll template in 3e that you could tweak and apply to any creature you want ot have some Troll-ness, link here: https://www.realmshelps.net/monsters/templates/halftroll.shtml

I love the way that Trolls in the animated series Hilda turn into stone under the sun, and then turn back to Troll when the sun goes down. I have used this for my game, though Trolls haven't come up yet!

I have mine hiding under bridges, because it keeps the sun off of them. They roll in mud to block the sun, and fight blind if they have to to spare their eyes. They are tribal in my world, taking the role Orc take in many older fantasy worlds. They are also fiercely strong and wickedly fast, and I decided that the best way to convey them as a threat to the party was to bake in an ability to throw people into their statblocks. Facing a troll is all well and good when the paladin and barbarian stand between it and the wizard, but when they get flung 30ft. away, suddenly the Wizard is getting a little afraid!

They act as ambushers in my world, and also are stealthy - they will sneak into towns to steal children to eat. Yep, they're irredeemable monsters in my world!

Recently saw folklorre saying that passing under a bridge is how you get to the world of trolls, so there's another bit I might work into my world!

Hilda is literally the most fantastic thing to come out of television since ... well, I don't know since when. Since forever, possibly. 

I agree.

Trolls are wild, animalistic brutes. They are immensely adaptable and insanely difficult to slay because of the amount of life in them. When life was getting pasted around, trolls got a double portion. Their cells are simply overflowing with life and it frequently bursts out in the form of random mutations. It makes one wonder how something so fundamentally alive could be such a destructive force of death. 

This abundance of life makes their blood, meat, and bones incredibly valuable. It gives their parts a wide variety of alchemical and arcane uses and many a magician will pay a pretty penny for a piece of troll. 

To answer this demand, somebody must supply. In the spirit of capitalism, Trollslayers have risen to the occasion and have made it their business to bring down these dangerous creatures. They usually form parties of at least 12 members with each member assigned a different roll to play in the hunt.

Sniffers breed specialized troll hounds that seek out their prey. The troll hounds are massive dogs with heavy builds yet quick feet. Once they have found their quarry the hounds rush the troll, avoiding the beasts blows with their nimble agility and agitating it by taking chunks out with their powerful jaws. They also serve as a distraction, giving the hunters openings to strike and drawing its attention away from them. While their dogs are let loose, the Sniffers will usually fall back with a bow and join the archers. 

Archers typically stay farther back near the Torchers. They use their ranged weapons to whittle away at the troll's strength from a distance and they usually light their arrows with the Torcher's flames to deal more damage. 

Torchers are another key role in the hunt. They typically wield a brightly lit torch in each hand and use the flames to shield the archers and restrict its movement. They will often set fire to surrounding brush to further constrict their prey. They also frequently start forest fires to drive out any trolls lurking in deep brush. 

Riders typically ride atop armored mounts and sink barbed lances into the troll's hide. They will also carry a large sword for when they are caught close enough to the beast to strike. They are often the ones who receive the glory for their kills.

Thanks to natural selection, Trolls have begun getting smarter. Now, the most intelligent will hide under bridges and ask riddles to adventurers. since most parties have a wizard or smart person, the party will solve the riddles and pass, not engaging in a brutal battle against said troll. Win-Win. And, the troll can eat any uneducated farmer who gets it wrong.

They get along well with monsters due to them not being caught up in silly things like 'morals' and most monster tribes don't care if a troll eats the occasional weakling. Why they love treasure? It looks pretty. Despite being ravenous monsters, Trolls love to feel pretty. 

As for origin? Like most things in dnd, it can be chalked up to a random god doing things for fun or spite. 

Another take on the same story - the one that trolls are simply too hideous for natural procreation to happen - is that they multiply by division. That originally there was just one troll, and all trolls are essentially clones of that guy. Now, for division to happen, you need something very specific to happen. Lobbing off the head or hand of a troll doesn't mean it'll grow into two (although that could have been an option).

No, what needs to happen is that the troll needs to be split, somehow, through the heart. Each half of the heart will regenerate, and then regenerate the troll. 

Obviously, trolls themselves are simply way too dumb to realise this fact. Otherwise, they'd be doing it to themselves out of spite. Sure, too many trolls would be inconvenient for the trolls themselves, but they could always just duke it out amongst themselves after they'd eaten everyone else.

But who was this first troll? Well, truthfully, I dunno. But let me think about it, something will come up =)

Quote from Acromos >>

Another take on the same story - the one that trolls are simply too hideous for natural procreation to happen - is that they multiply by division. That originally there was just one troll, and all trolls are essentially clones of that guy. Now, for division to happen, you need something very specific to happen. Lobbing off the head or hand of a troll doesn't mean it'll grow into two (although that could have been an option).

No, what needs to happen is that the troll needs to be split, somehow, through the heart. Each half of the heart will regenerate, and then regenerate the troll. 

Obviously, trolls themselves are simply way too dumb to realise this fact. Otherwise, they'd be doing it to themselves out of spite. Sure, too many trolls would be inconvenient for the trolls themselves, but they could always just duke it out amongst themselves after they'd eaten everyone else.

But who was this first troll? Well, truthfully, I dunno. But let me think about it, something will come up =)

 Trollgatha, the Mother Troll. (gonna make stats for her later.)

Quote from Rob76 >>

From that, I'm still tinkering with the idea that enviromental conditions combined with a trolls regeneration will produce odd "evolutions" in Trolls, So a Troll that drowns effectielly drops to zero hit points and regenrates back to one hit point over and over again and eventually the troll develops gills, trolls that are subjected to fire repeatedly eventually become resistant to it etc.

I do this all the time. Trolls that live by the ocean are very different from swamp trolls who are very different from desert trolls, etc

In fact, I can't remember the last time I threw an off-the-rack troll at a party. They always have some sort of mutation -- different resistances, different attacks, different movement abilities, something

Quote from Selleck >>

 Trollgatha, the Mother Troll. (gonna make stats for her later.)

 Please do - I will wait full of excited expectation, like a child on christmas morning.